Radiation beam recording mediums may be generally divided into two types. First, recordings may be made by projecting a radiation beam into a record coated with a photographic layer or a photoresist layer. The image immediately produced in this type of layer is latent, that is, further processing is necessary prior to the time the record may be "played back".
A second type of radiation-sensitive medium provides an immediate change in the optical properties of the recording medium. This latter type of medium is generally referred to as a direct read after write or DRAW material. Examples of such DRAW materials are thin layers of metals such as rhodium or berillum, metal compounds such as arsenic selinide, bismuth compounds, amorphus semiconductors, and photochromic materials such as KCl with N.sub.a F.sub.a centers.
These materials experience a physical change such as melting or evaporation, or a chemical reaction such as decomposition or combination in response to a radiation beam.
The recording process for any of the above types of record mediums involves manufacturing the blank record, recording the information thereon, developing if necessary and encasing the record to protect the same from damage. Between the stages of manufacturing the blank record and encasing the record the radiation-sensitive surface is subject to damage by scratching or nicking due to mishandling. Furthermore, some recording media are subject to chemical contamination prior to recording from handling or from atmospheric pollution.
It is therefore desirable to protect the material in some manner after the blank record is manufactured. An apparently obvious solution would be to coat one side of the transparent disc with radiation-sensitive materials and to coat the sensitive materials with a protective layer. Unfortunately, while the protective layer would prevent scratches and nicks prior to recording, in the case of non-DRAW recording materials the protective layer must be removed prior to development of the sensitive material, while in the case of most DRAW materials, where the recording process generally involves melting and evaporation or chemical reactions producing gaeous by-products, the protective layer would interfere with the physical and chemical processes.